In general, an LED module may be basically divided into a DC-operated LED module and an AC-operated LED module depending on the type of power that is received in order to operate the LED module.
FIG. 1 is a circuit diagram of a conventional AC-operated LED module.
As shown in FIG. 1, the conventional circuit 1 for operating an AC LED module includes an AC power source 10, a first LED module 20, a second LED module 30, and a resistor 40.
The conventional circuit 1 for operating an AC LED module will be described below with reference to FIG. 1. First, when an input voltage Vac supplied by the AC power source 10 is applied in a positive direction (that is, for a positive half cycle of the AC voltage), a current flows in the order of R1, D1, D2, ˜, Dn−1, Dn, Dn+1, Dn+2, ˜, D2n−1, and D2n, and thus the first LED module 20 and the second LED module 30 are operated. When the input voltage supplied by the AC power source 10 is applied in a negative direction (that is, for a negative half cycle of the AC voltage), a current flows in the order of R1, D2n, D2n+1, ˜, Dn+2, Dn+1, Dn, Dn−1, ˜, D2, and D1, and thus the first LED module 20 and the second LED module 30 are operated.
In this case, the magnitude of the current may be determined by the resistor 40 connected between the output side of the AC power source 10 and the input side of the first LED array 20.
As described above, the conventional circuit 1 for operating an AC LED module is advantageous in that it has a simple configuration, but is problematic in that the input voltage from the AC power source 10 needs to be always supplied as a constant voltage in order to supply a constant current to the first LED module 20 and the second LED module 30, and in that a section in which a current flows is narrow because the current flows when the input voltage is higher than the forward voltage of 2n LEDs, thereby lowering a power factor.
Furthermore, the conventional circuit 1 for operating an AC LED module using only the resistor 40 is problematic in that a flicker phenomenon, that is, a phenomenon in which light flickers, may be generated because the operation of a constant current for securing the lifespan and optical characteristics of an LED device is very limited, and in that the lifespan of an LED device is reduced because the operation voltage of the LED device that varies depending on temperature and the forward loss voltage of the LED device cannot be maintained.